The present invention relates to 360-degree image/video content processing, and more particularly, to method and apparatus having a video encoding function with syntax element signaling of rotation information of content-oriented rotation applied to a 360-degree image/video content represented in a projection format and associated method and apparatus having a video decoding function.
Virtual reality (VR) with head-mounted displays (HMDs) is associated with a variety of applications. The ability to show wide field of view content to a user can be used to provide immersive visual experiences. A real-world environment has to be captured in all directions resulting in an omnidirectional video corresponding to a viewing sphere. With advances in camera rigs and HMDs, the delivery of VR content may soon become the bottleneck due to the high bitrate required for representing such a 360-degree image/video content. When the resolution of the omnidirectional video is 4K or higher, data compression/encoding is critical to bitrate reduction.
In general, the omnidirectional video corresponding to a viewing sphere is transformed into a sequence of images, each of which is represented by a 360-degree Virtual Reality (360 VR) projection format, and then the resulting image sequence is encoded into a bitstream for transmission. However, the original 360-degree image/video content represented in the 360 VR projection format may have poor compression efficiency due to moving objects split and/or stretched by the employed 360 VR projection format. Thus, there is a need for an innovative design which is capable of improving compression efficiency of a 360-degree image/video content represented in a 360 VR projection format.